Destructive oxidation of organic materials in an aqueous medium has been employed because it provides a useful process for reducing the chemical oxygen demand of organics in water systems. This avoids the need to de-water the system in order to burn in a fuel system the organics. British patent 706,686 discloses a self-sustaining process for the destructive oxidation of organic materials in an aqueous medium. The system operates at a temperature above 450.degree. F. and a pressure sufficient to maintain the water in liquid form so as to cause the organic material to be oxidized. Such pressures may be in the range of 1400 to 1500 pounds per square inch and the temperatures may be as high as 625.degree. F.
Catalysts have been used in the system to catalyze the oxidation reaction, such as disclosed in U.S. Pat. No. 2,690,425. The system is operated at temperatures in the range of 100.degree. C. to 350.degree. C. under pressures of between 400 to 2500 pounds per square inch.
The reactor design for the wet oxidation system has been provided in many forms, such as disclosed in U.S. Pat. No. 3,870,631. The reactor is horizontally oriented and has several compartments to provide a series reactor arrangement. Agitators are used to provide a rubbing or abrasive contact between the combustible organic matter and the oxygen over a maximum area by reason of the high state of movement during agitation by the agitators. The agitators are power intensive in view of the speeds at which they must rotate to generate the degree of agitation required in the wet oxidation process of that patent, e.g. they may be rotated at speeds of 1300 rpm.
Another approach in agitating a liquid system is to use ultrasonic energy as disclosed in U.S. Pat. No. 4,013,552. Ultrasonic energy is transmitted to sewage which is at standard temperature and pressure. This treatment reduces the liquid particle size and enrobes the reduced water particles with air to enhance the biochemical oxidation by the aerobic bacteria. However, this patent does not contemplate the use of ultrasonic energy in the chemical oxidation of organic matter. Although U.S. Pat. No. 4,003,832 discloses the use of ultrasonic energy in chemical oxidation of organic matter, this patent requires the use of large concentrations of ozone in the area of the ultrasonic energy generator.
U.S. Pat. No. 4,155,848 discloses a vertical reactor tower for use in the wet oxidation of organic matter. The vertical tower has an outer cylindrical vessel with a smaller diameter concentric tube therein. The introduced organic matter and oxygen are circulated downwardly of the annular portion of the vessel and upwardly of the interior of the reactor core. The oxygen is introduced into the base of the inner tube so that in flowing upwardly, it causes a circulation of the aqueous medium in the system. This requires considerably increased supply of compressed air to cause the necessary circulation. The process, therefore, becomes cost ineffective because of the high capital and energy intensive system needed to compress this air. The system is normally operated at temperatures in the range of 250.degree. C. to 374.degree. C. The pressure is high enough to maintain the effluent in liquid phase.
U.S. Pat. No. 4,604,215 and 4,793,919 disclose reactor systems which have a reactor tower comprising an inner tube and an outer shell. A static mixer vane arrangement is provided within the inner tube. A circulating device is provided at the base of the reactor tower which withdraws liquid from the outer annular space and directs it upwardly of the inner space to thereby develop circulation of organic aqueous liquids through the reactor tower. Treated waste and liquid is withdrawn solely from the top of the tower and which is passed through a heat exchanger before the treated liquid is released. It is suggested in these patents that this arrangement can be set up in series where the treated waste liquid and gas together as withdrawn from the top of one tower are introduced to the side of the next tower. Circulation of the aqueous suspension is achieved individually within each tower. Although this system works very well with most types of aqueous suspensions, it has been found that the efficiencies are not quite as high as desired and hence a need for overall improved performance.
It is therefore an object of this invention to provide a reactor system in which the process is carried out in a manner to optimize the performance of the wet oxidation process carried out in reactors of the type described in the aforementioned U.S. Pat. Nos. 4,604,215 and 4,793,919.